Research Of Control Technology For Sensorless And Brushless DC Motor

With the rapid development of the high performance permanent magnet materials, microelectronic technology, automatic control technology and electric power and electronics technology, especially high-power semiconductor components, permanent magnet synchronous motor has developed fast. Brushless DC motor has been paid more attention as its superior characteristics of speed control, small size, light weight, high efficiency, small turnning inertia, and no loss excitation.Brushless DC motor has great significance for improving product performance, saving energy, improving people's living standards. But position sensors not only increase hardware investments of small-capacity equipment, but also undermine brushless DC motor fastness, simplicity and widespread application and affect the reliability,the accuracy, and manufacturing craft requirements . Therefore, the research of sensorless brushless DC motor control has good application value and prospects.First the experimental hardware platform of the sensorless brushless DC motor has been established, including the main circuit, the peripheric circuit, the drive circuit and the design of reliability. A modified method of three-step start has been raised according to the advantage and disadvantage of common sensorless BLDCM start technology ,which adapts to the changes of load.Then the dissertation presents its own BEMF method and lagging 90-a commutation method through the analysis of common detection methods of sensorless brushless DC motor magnetic pole position and the error caused by the filtering, to achieve more accurate commutation.The compensation methods of the elimination of electromagnetic and all-time control are adopted and the reduced value of the torque ripple is calculated through the analysis of the motor torque and the deduction of motor torque ripple value. Finally the dissertation analyzes the current mode, voltage mode, the characteristics of five modulation methods and their affection to BEMF current and motor performance in detail.Good research results have been received on the ST7FMC1K2 experimental platform,which improve the characteristics of starting, reduce ripple,motor dithering and noise, enhance the system reliability and the motor characteristics, increase the life of the motor.